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Lanthionine cross-linking

NMR studies have been used to resolve the structures of several lantibiotics.38 Cinnamycin and duramycin have been shown to adopt U-shaped globular structures, resulting from their intertwined lanthionine cross-links, which include a head-to-tail thioether.38 The structures are amphipathic, with hydrophobic residues clustered around the bend of the U-shaped and hydrophilic residues located around the termini. Likewise, the type B peptides mersacidin and actagardine adopt well-defined globular folds in methanol and water acetonitrile mixtures.39 40... [Pg.117]

Other conversions to unnatural residues occur when most proteins are exposed to high pH (80, 81,82). The high pH causes a -elimination of a cystine (see Figure 16) or O-substituted serine or threonine, with the formation of a dehydroalanine or a dehydro-a-aminobutyrate. Such products are subject to nucleophilic attack by the e-amino group of a lysine to form a cross-linkage, such as lysinoalanine, or attack by cysteine to form lanthionine. Walsh et al. (81) have taken advantage of the formation of these cross-links to produce avian ovomucoids that have nonreducible cross-links and have lost the antiprotease activity of one of their two inhibitory sites (see Figure 17). [Pg.38]

Nutritional and Physiological Effects of Alkali-Treated Proteins. The first effect of the alkaline treatment of food proteins is a reduction in the nutritive value of the protein due to the decrease in (a) the availability of the essential amino acids chemically modified (cystine, lysine, isoleucine) and in (b) the digestibility of the protein because of the presence of cross-links (lysinoalanine, lanthionine, and ornithinoalanine) and of unnatural amino acids (ornithine, alloisoleucine, / -aminoalanine, and D-amino acids). The racemization reaction occurring during alkaline treatments has an effect on the nitrogen digestibility and the use of the amino acids involved. [Pg.113]

Alkali has long been used on proteins for such processes as the retting of wool and curing of collagen, but more recently it has received interest from the food industry. Alkali can cause many changes such as the hydrolysis of susceptible amide and peptide bonds, racemization of amino acids, splitting of disulfide bonds, beta elimination, and formation of cross-linked products such as lysinoalanine and lanthionine. [Pg.16]

P. T. Speakman (1961) obtained a linear relationship between set in borate solutions and [loss of cystine] Using Flory s (1956) expression for the isotropic length of a cross-linked polymer he concluded that lan-thionine cross-linkages determined the set length of the fibers. Two main assumptions were made (1) that cystine loss equals the lanthionine formed, and (2) that the fiber is an elastomer in hot water. Other attempts to investigate the formation of covalent bonds other than disulfides are equivocal (P. T. Speakman 1957,1958), as insufficient information is known concerning the chemical and physical effects of boiling bisulfite solutions on wool. [Pg.318]

The action of alkalis on the disulphide bond is complex and is accompanied by the formation of inorganic sulphides. The bond is severed, but new cross-links arc formed of the type —CHg-S.CHj—, as demonstrated by Horn, Jones, and Ringel J. Biol. Chem., 1941, 138, 141), who isolated lanthionine from alkali-treated wool. [Pg.91]

Tolgyesi and Fang [68] have found that alkaline amine solutions react differently with human hair. With human hair, all amines examined, including pentyl amine, compete less effectively with the amino and mercaptan residues of the hair for the dehydroalanine intermediate. As a result, more lanthionine and lysinoalanine cross-links form than amine adduct, when human hair is the substrate. This is probably because diffusion rates are slower into human hair, decreasing the effective concentration of free amine in the fibers. Therefore, these species cannot compete as effectively for the dehydroalanine intermediate therefore, lanthionine and lysinoalanine are formed. [Pg.127]

A test to discover whether wool has been damaged in processing is to determine the fraction of the wool that dissolves under standard conditions in a solution containing urea, as a hydrogen bond breaker, and a reducing agent, usually bisulfite. Add damage increases the solubility of treated, compared with untreated wool, because add hydrolyzes peptide bonds in the protein chains. Alkali treatment decreases the solubility, because redudble cystine residue disulfide cross-links are slowly replaced by nonreducible lanthionine and lysinoalanine crosslinks in alkali (see Section 5.3.4). [Pg.358]

Cystine residues in wool are attacked by alkali [13,242], and two new cross-links lanthionine and lysinoalanine—are formed. A mechanism for the reaction of cystine residues with alkali has been suggested. [Pg.359]

Treatment of wool with water or neutral buffer solution [13,242] at temperatures above 50°C causes the formation of lanthionine and lysinoalanine residue cross-links and, therefore, decreases the solubility of wool in urea-bisulfite solutions. When wool is heated in water in a sealed tube, it contracts at temperatures between 128 and 140°C, depending on the rate of heating. [Pg.360]

When wool is treated with alkali or hot water in the absence of added agents, cross-linking also occurs, to form lanthionine and lysinoalanine [253]. [Pg.362]

Dry heat in air causes less damage to wool than wet heat does [13,267,268]. Above 140°C, yellowing or scorching occurs lanthionine, lysinoalanine, and isopeptide cross-links are formed, and solubility in urea-bisulfite solution decreases. Cysteic acid residues are formed... [Pg.363]


See other pages where Lanthionine cross-linking is mentioned: [Pg.247]    [Pg.269]    [Pg.287]    [Pg.300]    [Pg.117]    [Pg.48]    [Pg.31]    [Pg.191]    [Pg.89]    [Pg.277]    [Pg.350]    [Pg.368]    [Pg.359]    [Pg.364]    [Pg.39]   
See also in sourсe #XX -- [ Pg.368 ]

See also in sourсe #XX -- [ Pg.368 ]




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Lanthionine

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